The field of the present disclosure relates to optical encoding of data. In particular, distributed diffractive structures (i.e. sets of diffractive elements) are formed in or on an optical medium for encoding the data.
Optical recording media in the form of compact disks (CDs), digital versatile discs or digital video discs (DVDs), and more advanced format optical discs play an important role in the distribution of software, data, music, video, or other content. Such discs typically include a data layer wherein localized micron- or sub-micron-scale marks (typically recessed pits, raised bumps, index or density variations, or other suitable marks) are optically or mechanically written, which is overlaid with a substantially transparent protective layer. Upon readout, a reading laser beam is typically focused through the transparent layer to a spot of a size similar to the size of the data marks when it reaches the data layer, and a portion of the reading beam is redirected by the data mark (usually back-reflected). Upon entering the transparent protective layer, the reading laser spot size is typically substantially larger, i.e. many times the size of data marks of the data layer (tens or hundreds of microns or more). The larger size of the reading laser spot as it enters the transparent protective layer reduces the effect of dust, scratches, nicks, or other imperfections or irregularities on the exterior surface of the disc. The light back-reflected from the data layer is detected and monitored for variations as the disk spins and the focused reading laser spot sweeps across the data marks and areas of the disc between the data marks. Variations in the detected, back-reflected optical signal arise from differences between the back-reflected reading laser beam reflected from the data marks and from areas between the data marks. Such differences may be differences of back-reflected power or intensity, back-reflected beam size or geometry, or other selected property of the back-reflected beam.
An exemplary geometry of a single data layer 100 and its protective transparent overcoat layer 102 are shown in FIG. 1. The optical disk may be multi-sided or have a more complex configuration, but for convenience of exposition only, only a single data layer and its protective transparent coating are described. The methods and devices disclosed herein may be implemented to single-layer or multi-layer or other advanced format optical discs provided they have surficial or interfacial regions surrounding the data layer through which read lasers may be transmitted. A data layer may also be protected or overcoated on the back (i.e. from the non-read side) although such details are not of particular significance for the present disclosure. Localized data marks 101 may be produced as a part of a molding or stamping process used to make the disc, by spot-based laser writing, or other means. The localized data marks 101 may typically comprise indentations of some depth into the non-read side of transparent layer, which therefore appear as bumps from the read side of the disc. The data marks thus formed on the non-read side of the transparent layer may be overcoated on the non-read side with a high or partial reflective material. A reading-laser beam 103 is shown focused onto one of the data marks 101. Any other suitable arrangements or adaptations of the data marks, data layer, or transparent protective layer may be employed while implementing the structures, methods, arrangements, or adaptations disclosed or claimed herein. The particular detailed nature of typically-employed data marks does not limit application of the methods and devices disclosed or claimed herein.
The data marks 101 are shown as bumps (from the read side) in FIG. 1. A copy of the disc can be made via optical writing where a sufficiently powerful laser beam is used to make optical marks on the data layer of a suitably sensitized blank disc. Commercial content from stamped, molded, or otherwise produced disc may typically be reproduced via a suitable focused-spot laser writer. The present disclosure describes distributed (i.e. non-localized) encoding of data on an optical disc by means that may be difficult to reproduce via a focused-spot laser writer. Data encoded as described in the present disclosure may be introduced in the same production process that produces standard localized data marks on the data layer or by alternate means such as secondary stamping, embossing, printing, e-beam writing, laser pattern generation, and so forth.
Various embodiments, implementations, and adaptations of optical waveguides, diffractive element sets, or distributed diffractive structures are disclosed in:                Application Ser. No. 11/376,714 filed Mar. 14, 2006 in the names of Thomas W. Mossberg, Dmitri lazikov, and Christoph M. Greiner (now U.S. Pat. No. 7,349,599);        Application Ser. No. 11/371,339 filed Mar. 7, 2006 in the names of Dmitri lazikov, Christoph M. Greiner, and Thomas W. Mossberg (now U.S. Pat. No. 7,327,908 issued Feb. 5, 2008);        Application Ser. No. 11/361,407 filed Feb. 23, 2006 in the name of Thomas W. Mossberg (now U.S. Pat. No. 7,116,453 issued Oct. 3, 2006);        Application Ser. No. 11/334,039 filed Jan. 17, 2006 in the names of Thomas W. Mossberg, Christoph M. Greiner, and Dmitri lazikov;        Application Ser. No. 11/298,290 filed Dec. 9, 2005 in the names of Thomas W. Mossberg, Dmitri lazikov, and Christoph M. Greiner (now U.S. Pat. No. 7,330,614 issued Feb. 12, 2008);        Application Ser. No. 11/280,876 filed Nov. 15, 2005 in the names of Christoph M. Greiner, Dmitri lazikov, and Thomas W. Mossberg;        Application Ser. No. 11/239,540 filed Sep. 28, 2005 in the name of Thomas W. Mossberg (now U.S. Pat. No. 7,009,743 issued Mar. 7, 2006);        Application Ser. No. 11/213,345 filed Aug. 25, 2005 in the names of Christoph M. Greiner, Dmitri lazikov, and Thomas W. Mossberg (now U.S. Pat. No. 7,120,334 issued Oct. 10, 2006);        Application Ser. No. 11/210,439 filed Aug. 23, 2005 in the names of Dmitri lazikov, Christoph M. Greiner, and Thomas W. Mossberg (now U.S. Pat. No. 7,359,597 issued Apr. 15, 2008);        Application Ser. No. 11/155,327 filed Jun. 16, 2005 in the names of Christoph M. Greiner, Thomas W. Mossberg, and Dmitri lazikov (now U.S. Pat. No. 7,190,858 issued Mar. 13, 2007);        Application Ser. No. 11/076,251 filed Mar. 8, 2005 in the name of Thomas W. Mossberg (now U.S. Pat. No. 7,062,128 issued Jun. 13, 2006);        Application Ser. No. 11/062,109 filed Feb. 17, 2005 in the names of Christoph M. Greiner, Thomas W. Mossberg, and Dmitri lazikov (now U.S. Pat. No. 7,181,103 issued Feb. 20, 2007);        Application Ser. No. 11/055,559 filed Feb. 9, 2005 in the names of Christoph M. Greiner, Thomas W. Mossberg, and Dmitri lazikov (now U.S. Pat. No. 7,123,794 issued Oct. 17, 2006);        Application Ser. No. 11/021,549 filed Dec. 23, 2004 in the names of Dmitri lazikov, Christoph M. Greiner, and Thomas W. Mossberg (now U.S. Pat. No. 7,260,290 issued Aug. 21, 2007);        Application Ser. No. 10/998,185 filed Nov. 26, 2004 in the names of Dmitri lazikov, Christoph M. Greiner, and Thomas W. Mossberg (now U.S. Pat. No. 6,993,223 issued Jan. 31, 2006);        Application Ser. No. 10/989,244 filed Nov. 15, 2004 in the names of Christoph M. Greiner, Thomas W. Mossberg, and Dmitri lazikov (now U.S. Pat. No. 6,961,491 issued Nov. 1, 2005);        Application Ser. No. 10/989,236 filed Nov. 15, 2004 in the names of Christoph M. Greiner, Dmitri lazikov, and Thomas W. Mossberg (now U.S. Pat. No. 6,965,716 issued Nov. 15, 2005);        Application Ser. No. 10/923,455 filed Aug. 21, 2004 in the names of Thomas W. Mossberg, Dmitri lazikov, and Christoph M. Greiner (now U.S. Pat. No. 7,054,517 issued May 30, 2006);        Application Ser. No. 10/898,527 filed Jul. 22, 2004 in the named of Dmitri lazikov, Christoph M. Greiner, and Thomas W. Mossberg (now U.S. Pat. No. 7,194,164 issued Mar. 20, 2007);        Application Ser. No. 10/857,987 filed May 29, 2004 in the names of Lawrence D. Brice, Christoph M. Greiner, Thomas W. Mossberg, and Dmitri lazikov (now U.S. Pat. No. 6,990,276 issued Jan. 24, 2006);        Application Ser. No. 10/842,790 filed May 11, 2004 in the names of Thomas W. Mossberg, Christoph M. Greiner, and Dmitri lazikov (now U.S. Pat. No. 6,987,911 issued Jan. 17, 2006);        Application Ser. No. 10/798,089 filed Mar. 10, 2004 in the names of Christoph M. Greiner, Thomas W. Mossberg, and Dmitri lazikov (now U.S. Pat. No. 6,823,115 issued Nov. 23, 2004);        Application Ser. No. 10/794,634 filed Mar. 5, 2004 in the names of Dmitri lazikov, Thomas W. Mossberg, and Christoph M. Greiner (now U.S. Pat. No. 6,985,656 issued Jan. 10, 2006);        Application Ser. No. 10/740,194 filed Dec. 17, 2003 in the names of Dmitri lazikov, Thomas W. Mossberg, and Christoph M. Greiner (now U.S. Pat. No. 7,224,855 issued May 29, 2007);        Application Ser. No. 10/653,876 filed Sep. 2, 2003 in the names of Christoph M. Greiner, Dmitri lazikov, and Thomas W. Mossberg (now U.S. Pat. No. 6,829,417 issued Dec. 7, 2004);        Application Ser. No. 10/602,327 filed Jun. 23, 2003 in the name of Thomas W. Mossberg (now U.S. Pat. No. 6,859,318 issued Feb. 22, 2005);        Application Ser. No. 10/229,444 filed Aug. 27, 2002 in the names of Thomas W. Mossberg and Christoph M. Greiner (now U.S. Pat. No. 6,678,429 issued Jan. 13, 2004);        Application Ser. No. 09/843,597 filed Apr. 26, 2001 in the name of Thomas W. Mossberg (now U.S. Pat. No. 6,965,464 issued Nov. 15, 2005);        Application Ser. No. 09/811,081 filed Mar. 16, 2001 in the name of Thomas W. Mossberg (now U.S. Pat. No. 6,879,441 issued Apr. 12, 2005).        
Application Ser. No. 11/376,714 is hereby incorporated by reference as if fully set forth herein. Application Ser. No. 11/376,714 and many of the other references listed above are indicative of the state of the art for forming diffractive elements. Some of these cited references describe diffractive elements formed in a one- or two-dimensional optical waveguide, wherein the input or output optical signal propagates in the waveguide. Some of these cited references describe diffractive elements forming surface gratings, wherein both input and output optical signals propagate as diffraction-guided optical beams. For one or more of the references cited hereinabove, it may be the case that the devices, structures, embodiments, implementations, adaptations, procedures, or techniques disclosed therein may be employed, within the scope of the present disclosure or appended claims, for optical encoding of data.